4:16 Reconstruction of complex craniocervical pathology with transarticular screws: assessment of long-term follow-up and quantitative evaluation of screw accuracy by computed tomography

Abstract

Purpose of study: Transarticular screws are an important option for managing C1–C2 instability, although long-term follow-up on efficacy, safety and application to complex occipitocervical reconstructions is required. To address these issues, we present our experience with transarticular screw fixation in 51 consecutive, prospective cases with a mean follow-up of over 2 years.Methods used: Indications for surgery included trauma (n=23), rheumatoid arthritis (n=13), failed fusion (n=12), degenerative instability (n=3), osteomyelitis (n=1) and os odontoidum (n=1). A C1–C2 fusion alone was performed in 37 cases, and transarticular screws were used as part of a complex reconstruction in 14 cases. Ninety-eight screws were positioned; four patients had a single C1–C2 screw. All cases were evaluated by lateral flexion-extension films. Postoperative computed tomography (CT) with thin cut reconstruction was obtained in 31 cases (60 screws). An index of relative anterior/posterior subluxation was measured on midline sagittal reconstructions.of findings: There were no neurological complications or vertebral artery injuries. A solid fusion was obtained in 46 of 51 cases with four stable fibrous unions and one asymptomatic pseudarthrosis. By CT criteria, screws were in excellent (n=20), good (n=17), acceptable (n=14) and poor (n=2) position. We found a strong correlation between greater than 4 mm of C1–C2 posterior subluxation and nonoptimal screw position (p<.001).Relationship between findings and existing knowledge: The findings in the present study validate the use of transarticlar screw fixation to manage complex craniocervical problems including revision and rheumatoid cases. The zero incidence of neurovascular injury compares favorably with published series that quote up to a 1.8% incidence of vertebral artery injury.Overall significance of findings: Transarticular screws represent an important technique to stabilize the C1–C2 joint and with experience can be placed with minimal risk. Cases of atlantoaxial instability with greater than 4 mm of nonreducible posterior subluxation are associated with poor fixation and should be considered a relative contraindication for this technique.Disclosures: Device or drug: transarticular screw fixation. Status: investigational.Conflict of interest: Michael Fehlings, grant research support, Synthesspire, Medtronic Sofamor Danek.